This can lead to less government and council funding for areas that are already struggling.

But, for 2018 there's a huge push by Statistics New Zealand to make sure everyone is counted this year.

Clint Hinga has 150 convictions and spent 12 years behind bars, he's never taken part in the Census because he was on the run from the cops.

"Who else I was associated with me they could use that data and information that I was giving over to find me," he said.

Now a family man with a steady job, he's taking part in Census for the first time in 2018.

"It's actually for our community for the people to get another perspective of how many people are in the homes so they know where to put their money," he said.

Most of the country takes part but the three percent that don't, like Mr Hinga, is the big concern.

Places like Manukau where Mr Hinga works are among those areas where people are less likely to fill out a census form.

Lower socioeconomic areas and areas where there are more minority groups like Māori and Pacific are far less likely to participate than pākehā.

What that means is these people are under-represented in the statistics and therefore under-represented when it comes to the government and council's dishing out the money.

Counties Manukau Health documents estimates 24,000 people didn't take part in the 2013 Census in that area.

That means they're down $50 million in funding.

"That would provide a lot more service to the community in just health, operations, dental care," said Dr Vanessa Thornton, acting chief medical officer for Counties Manukau Health.

There are a number of reasons why people are frightened of filling out a census including a fear the information will be passed on to debt collectors or over stayers worried immigration will catch them.

But Statistics New Zealand says all of the information gathered is used anonymously and as part of its push to capture the three percent they've been going to events to spread the word.